Other Links

Proteins Protect Insects From Cold

One of the major reasons insects are so successful is because they have many
physiological and biochemical mechanisms that protect them against
environmental stressesespecially, freezing temperatures.

Many insects, including the common house fly and the seemingly ever-present
fruit fly, produce specific proteins that offer them protection when
temperatures dip below freezing. Scientists have yet to piece together exactly
how these proteins function but have linked the accumulation of
low-molecular-weight compounds with increased cryoprotection.

This tiny biting insect, known as a "no-see-em," transmits
bluetongue virus. Bluetongue disease causes about $120 million in annual losses
to domestic livestock producers, mainly in lost exports to countries that do
not have the disease.

"The quantity of proteins the insects produce is proportional to the
severity and duration of the cold," says Richard A. Nunamaker, an
entomologist at the Arthropod-borne Animal Diseases Research Laboratory in
Laramie.

Scientists say that C. variipennis produces the proteins during a
process called cold-hardening. This pre-conditions the insects to withstand
temperatures that would ordinarily prove fatal. Culicoides usually die
after a 2-hour exposure to 14° F, but if the insects are first acclimated
for 1 hour at 41° F, 98 percent of the adults survivesome for as
long as 3 days.

"The cold-hardening that we performed in our laboratory is similar to
weather conditions in a large portion of the United States. It is possible that
adult Culicoides could survive cold weather for longer than anyone
thought possible," says Nunamaker.

Some winter survivors may have been infected with bluetongue virus the
previous warmer season, thus providing a possible source of infection among
livestock the following spring. This potential for virus overwintering poses
significant problems for people who are trying to halt its transmission among
U.S. livestock.

"However, interrupting cold-hardening through genetic manipulation of
Culicoides may be an effective strategy to reduce the probability of
bluetongue virus survival through cold weather," says Nunamaker.  By
Dennis Senft, ARS.